diff --git a/Lib/test/test_frame.py b/Lib/test/test_frame.py new file mode 100644 index 00000000000..daabba801b1 --- /dev/null +++ b/Lib/test/test_frame.py @@ -0,0 +1,113 @@ +import gc +import sys +import unittest +import weakref + +from test import support + + +class ClearTest(unittest.TestCase): + """ + Tests for frame.clear(). + """ + + def inner(self, x=5, **kwargs): + 1/0 + + def outer(self, **kwargs): + try: + self.inner(**kwargs) + except ZeroDivisionError as e: + exc = e + return exc + + def clear_traceback_frames(self, tb): + """ + Clear all frames in a traceback. + """ + while tb is not None: + tb.tb_frame.clear() + tb = tb.tb_next + + def test_clear_locals(self): + class C: + pass + c = C() + wr = weakref.ref(c) + exc = self.outer(c=c) + del c + support.gc_collect() + # A reference to c is held through the frames + self.assertIsNot(None, wr()) + self.clear_traceback_frames(exc.__traceback__) + support.gc_collect() + # The reference was released by .clear() + self.assertIs(None, wr()) + + def test_clear_generator(self): + endly = False + def g(): + nonlocal endly + try: + yield + inner() + finally: + endly = True + gen = g() + next(gen) + self.assertFalse(endly) + # Clearing the frame closes the generator + gen.gi_frame.clear() + self.assertTrue(endly) + + def test_clear_executing(self): + # Attempting to clear an executing frame is forbidden. + try: + 1/0 + except ZeroDivisionError as e: + f = e.__traceback__.tb_frame + with self.assertRaises(RuntimeError): + f.clear() + with self.assertRaises(RuntimeError): + f.f_back.clear() + + def test_clear_executing_generator(self): + # Attempting to clear an executing generator frame is forbidden. + endly = False + def g(): + nonlocal endly + try: + 1/0 + except ZeroDivisionError as e: + f = e.__traceback__.tb_frame + with self.assertRaises(RuntimeError): + f.clear() + with self.assertRaises(RuntimeError): + f.f_back.clear() + yield f + finally: + endly = True + gen = g() + f = next(gen) + self.assertFalse(endly) + + @support.cpython_only + def test_clear_refcycles(self): + # .clear() doesn't leave any refcycle behin + with support.disable_gc(): + class C: + pass + c = C() + wr = weakref.ref(c) + exc = self.outer(c=c) + del c + self.assertIsNot(None, wr()) + self.clear_traceback_frames(exc.__traceback__) + self.assertIs(None, wr()) + + +def test_main(): + support.run_unittest(__name__) + +if __name__ == "__main__": + test_main()